This invention relates to a novel coupler for photography to be used as the material for color photography, particularly to a coupler for photography which forms a dye image excellent in fastness to heat, humidity and light.
After exposure is given to a light-sensitive silver halide photographic material, the material is subjected to color developing processing, whereby the oxidized aromatic primary amine color developing agent reacts with a dye forming coupler in the exposed region to form a dye, thereby forming a dye image.
Generally speaking, in such photographic method, the color reproduction method according to subtractive color system is used to form color images of yellow, magenta and cyan.
As the coupler for photography to be used for formation of yellow color image as mentioned above, there is, for example, an acylacetanilide type coupler. As the coupler for formation of magenta color image, there have been known, for example, pyrazolone, pyrazolobenzimidazole, pyrazolotriazole or indazolone type couplers. Further, as the coupler for formation of cyan color image, for example, phenol or naphthol type couplers are generally used.
The dye image thus obtained is desired to be not discolored or faded even when exposed to light, or stored under high temperature, high humidity for a long time.
However, the phenol type couplers and the naphthol type couplers which have been studied as the coupler for formation of cyan dye are not yet insufficient in such points as spectral absorption characteristics of the cyan dye image formed, heat resistance, humidity resistance and light resistance, etc., and various proposals have been made, including contrivances with respect to substituents, but no compound satisfying all of these has not yet been obtained.
Accordingly, the present inventors have progressed further study about the above-mentioned points, and consequently found a coupler for photography capable of forming a cyan dye image which does not cause color shift to heat, humidity and light, to accomplish the present invention.